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 HTMLParser Library $Name: v1_5 $ - A java-based parser for HTML
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The tags package contains specific tags.
<p>This package has implementations of tags that have functionality beyond the
capability of a generic tag. For example, the {@.html <META>} tag has methods
to get the {@link org.htmlparser.tags.MetaTag#getMetaContent CONTENT} and
{@link org.htmlparser.tags.MetaTag#getMetaTagName NAME}
attributes (although this could be done with generic attribute manipulation)
and an implementation of
{@link org.htmlparser.tags.MetaTag#doSemanticAction doSemanticAction}
that alters the lexer's encoding.</p>
<p>The classes in this package have been added in an ad-hoc fashion, with the
most useful ones having existed a long time, while some obvious ones are rather
new. Please feel free to add your own custom tags, and register them with the
{@link org.htmlparser.PrototypicalNodeFactory PrototypicalNodeFactory},
and they will be treated like any other in-built tag. In fact tags do not need
to reside in this package.</p>
<br><b>Custom Tags</b>
<p>Creating custom tags is fairly straight forward. Simply copy one of the
simpler tags you find in this package and alter it as follows.
<p>If the tag can contain other nodes, i.e. {@.html <h1>My Heading</h1>}, then
it should derive from (i.e. be a subclass of) {@link org.htmlparser.tags.CompositeTag}.
In this way it will inherit the
{@link org.htmlparser.scanners.CompositeTagScanner CompositeTagScanner}
and nodes between the start and end tag will be gathered into the list of
children. Most of the tags in this package derive from CompositeTag, and that
is why the nodes returned from the Parser are nested.</p>
<p>If it is a simple tag, i.e. {@.html <br>}, then it should derive from
{@link org.htmlparser.nodes.TagNode TagNode}. See for example
{@link org.htmlparser.tags.MetaTag}
or {@link org.htmlparser.tags.ImageTag}.</p>
<p>To be registered with {@link org.htmlparser.PrototypicalNodeFactory#registerTag},
and especially if it is a composite tag, the tag needs to implement
<code>getIds</code> which returns the UPPERCASE list of names for the tag
(usually only one), for example "HTML". If the tag can be smart enough to know
what other tags can't be contained within it, it should also implement
{@link org.htmlparser.nodes.TagNode#getEnders getEnders()} which returns the
list of other tags that should cause this tag to close itself, and 
{@link org.htmlparser.nodes.TagNode#getEndTagEnders getEndTagEnders()} which
returns the list of end tags (i.e. {@.html </xxx>}), other than it's own name, that
should cause this tag to close itself. When these 'ender' lists cause a tag to
end before seeing it's own end tag, a virtual end tag is created and 'inserted'
at the location where the end tag should have been. These end tags can be
distinguished because their {@link org.htmlparser.Node#getStartPosition starting}
and {@link org.htmlparser.Node#getEndPosition ending} locations are the same
(i.e. they take up no character length in the HTML stream).
<p>For example, the {@.html <OPTION>} tag from a form can be prematurely ended by
any of {@.html <INPUT>}, {@.html <TEXTAREA>}, {@.html <SELECT>},
or another {@.html <OPTION>} tag. These are the tags in the getEnders() list.
It can also be prematurely ended by {@.html </SELECT>}, {@.html </FORM>},
{@.html </BODY>}, or {@.html </HTML>}. These are the tags in the
getEndTagEnders() list.
<p>Other than that any functionality is up to you. You should note that
{@link org.htmlparser.Node#doSemanticAction doSemanticAction()} is called after
the tag has been completely scanned (it has it's children and end tag), but before
its siblings further downstream have been scanned. If transformation is your purpose,
this is the opportunity to mess around with the content, for example to set the link URL,
or lowercase the tag name, or whatever.
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